1. Field of the Invention
The present invention relates to an apparatus and a method for kneading components into an aromatic polycarbonate. More specifically, it relates to a kneading apparatus and method which have an excellent kneading effect, suppress coloration, crosslinking and gelation due to the residence of a resin and can obtain a product having a small content of foreign matter when components to be kneaded, such as a terminal OH group capping agent, catalyst deactivator, devolatilizing agent and resin additives are added to and kneaded into an aromatic polycarbonate. Particularly, it relates to a twin screw extruder for adding and kneading the above components into an aromatic polycarbonate and the improvement of the extruder.
2. Prior Art
Aromatic polycarbonates are widely used for various purposes due to their excellent mechanical properties such as impact resistance and transparency. Known methods for producing such aromatic polycarbonates include an interfacial polymerization method in which a dihydroxy compound and phosgene are directly reacted with each other, a melt polymerization method in which an ester exchange reaction between a dihydroxy compound and a carbonic acid diester is carried out under heating and reduced pressure, and the like.
An aromatic polycarbonate obtained by polymerization is generally kneaded with various components using an intermeshing twin screw extruder. In this kneading step, the coloration, crosslinking and gelation of the aromatic polycarbonate occur, and the content of foreign matter contained in the aromatic polycarbonate increases, thereby exerting a great influence upon the quality of a final product.
These problems are serious for an aromatic polycarbonate which has recently been used in optical recording media that is required high recording density and high accuracy, such as a DVD, MO and CDR because such problems as coloration and gelation have a direct influence upon the optical properties such as a block error rate and mechanical properties such as tensile strength, flexural strength and toughness of a final product.
It is an object of the present invention to provide a kneading apparatus and method for producing an aromatic polycarbonate which has an extremely small content of foreign matter and is free from residence deterioration such as coloration, crosslinking or gelation when the aromatic polycarbonate is to be kneaded with various components.